Data, voice, and other communication networks are increasingly using fiber optics to carry information. In a fiber optic network, each individual fiber is generally connected to both a source and a destination device. Additionally, along the fiber optic run between the source and the destination, various connections or couplings may be made on the optical fiber to adjust the length of the fiber. Each connection or coupling requires a connector and adaptor to align the fibers such that the light can transmit without interruption.
The connector in joining fiber ends, for example, has, as its primary function, the maintenance of the fiber ends in an abutting relationship such that the core of one of the fibers is axially aligned with the core of the other fiber to maximize light transmissions from one fiber to the other. Another goal is to minimize back reflections. An alignment can be extremely difficult to achieve, as a good alignment (low insertion loss) of the fiber ends is a function of the alignment, the width of the gap (if any) between the fiber ends, and the surface condition of the fiber ends, all of which, in turn, are inherent in the particular connector design. The connector must also provide stability and junction protection and thus it must minimize thermal and mechanical movement effects. These same considerations apply to arrangements where the fiber, terminated in a plug connector, is to be used with active or passive devices, such as, for example, computers or transceivers and the like.
There are numerous, different, connector designs in use for achieving low insertion loss and stability. Some example connectors may include, but are not limited to, SC, Dual LC, LC, ST and MPO connectors. In most of these designs, a pair of ferrules (one in each connector, or one in the connector and one in the apparatus or device), each containing an optical fiber end, are butted together end to end and light travels across the junction. Zero insertion loss requires that the fibers in the ferrules be exactly aligned, a condition that, given the necessity of manufacturing tolerances and cost considerations, is virtually impossible to achieve, except by fortuitous accident. As a consequence, most connectors are designed to achieve a useful, preferably predictable, degree of alignment.
Therefore, since the mechanical tolerances involved in terminating optical fiber are stringent in most applications, optical fiber is generally not terminated on site. In situations wherein optical fiber must be terminated on site, it may take a skilled technician between about 15 to 20 minutes to splice the fibers together using specialized splicing equipment. Optical fiber is therefore often provided in a range of different lengths, pre-terminated at both ends with a connector plug ready to plug into a matching receptacle.
In many installations, optical fiber cables are routed through a protective conduit that not only protects the cable, but also allows for rapid restoration methods when the conduit, fiber optic cable, or both are cut or damaged and replacement is necessary. Since pre-installed connectors are of an industry standard footprint, the fully assembled connectors may be too large to be pushed or pulled through microduct because of size constraints, as some microducts may have internal diameters of only about 6 mm, essentially large enough for the cables to fit through, but not a fully assembled connector.
While single and dual fiber connectors are of a smaller size and are more readily adaptable to fit through a conduit, it has also become desirable to provide partially assembled connectors for multi-fiber connectors, such as MPO connectors, that are partially pre-assembled with requisite tolerances, and that may be able to be pushed or pulled through a conduit. Any additional final assembly of the connector components may then be performed on site once the objective of delivering the fiber through a length of microduct has been achieved. Likewise, there is also a need for pre-assembled multi-fiber cables and cable connectors that have a footprint that allows for the pre-assembled cables to be inserted through minimal diameter conduit to thereby minimize the intrusion of placing the pathway or conduit for the fiber optic network, while also minimizing on-site assembly time and costs.